有谁知道以下错误日志的原因，请帮我解决这个问题。
[testng] org.openqa.selenium.firefox.NotConnectedException: Unable to connect to host 127.0.0.1 on port 7073 after 45000 ms. Firefox console output:
[testng] *** LOG addons.manager: Application has been upgraded
[testng] *** LOG addons.xpi: startup
[testng] *** LOG addons.xpi: Ignoring file entry whose name is not a valid add-on ID: /tmp/anonymous486500130836738733webdriver-profile/extensions/webdriver-staging
[testng] *** LOG addons.xpi: checkForChanges
[testng] *** LOG addons.xpi-utils: Opening XPI database /tmp/anonymous486500130836738733webdriver-profile/extensions.json
[testng] *** LOG addons.xpi: New add-on fxdriver@googlecode.com installed in app-profile
[testng] *** Blocklist::_loadBlocklistFromFile: blocklist is disabled
[testng] *** LOG addons.xpi-utils: Make addon app-profile:fxdriver@googlecode.com visible
[testng] *** LOG DeferredSave/extensions.json: Save changes
[testng] *** LOG DeferredSave/extensions.json: Save changes
[testng] *** LOG addons.xpi: New add-on {972ce4c6-7e08-4474-a285-3208198ce6fd} installed in app-global
[testng] *** LOG addons.xpi-utils: Make addon app-global:{972ce4c6-7e08-4474-a285-3208198ce6fd} visible
[testng] *** LOG DeferredSave/extensions.json: Save changes
[testng] *** LOG DeferredSave/extensions.json: Save changes
[testng] *** LOG addons.xpi: Updating database with changes to installed add-ons
[testng] *** LOG addons.xpi-utils: Updating add-on states
[testng] *** LOG addons.xpi-utils: Writing add-ons list
[testng] *** LOG DeferredSave/extensions.json: Starting timer
[testng] *** LOG DeferredSave/extensions.json: Starting write
[testng] *** LOG DeferredSave/extensions.json: Write succeeded
[testng] *** LOG addons.xpi-utils: XPI Database saved, setting schema version preference to 15
[testng] *** LOG addons.manager: shutdown
[testng] *** LOG addons.xpi: shutdown
[testng] *** LOG addons.xpi-utils: shutdown
[testng] *** LOG addons.xpi: Notifying XPI shutdown observers
[testng] *** LOG addons.manager: Async provider shutdown done
[testng] *** LOG addons.xpi: startup
[testng] *** LOG addons.xpi: Ignoring file entry whose name is not a valid add-on ID: /tmp/anonymous486500130836738733webdriver-profile/extensions/webdriver-staging
[testng] *** LOG addons.xpi: checkForChanges
[testng] *** LOG addons.xpi: No changes found
[testng]
[testng] at org.openqa.selenium.firefox.internal.NewProfileExtensionConnection.start(NewProfileExtensionConnection.java:118)
[testng] at org.openqa.selenium.firefox.FirefoxDriver.startClient(FirefoxDriver.java:250)
[testng] at org.openqa.selenium.remote.RemoteWebDriver.<init>(RemoteWebDriver.java:110)
[testng] at org.openqa.selenium.firefox.FirefoxDriver.<init>(FirefoxDriver.java:197)
[testng] at org.openqa.selenium.firefox.FirefoxDriver.<init>(FirefoxDriver.java:190)
[testng] at org.openqa.selenium.firefox.FirefoxDriver.<init>(FirefoxDriver.java:186)
[testng] at org.openqa.selenium.firefox.FirefoxDriver.<init>(FirefoxDriver.java:103)
[testng] at com.invient.ui.common.IFTestBase.init(Unknown Source)
[testng] at sun.reflect.GeneratedMethodAccessor9.invoke(Unknown Source)
[testng] at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[testng] at java.lang.reflect.Method.invoke(Method.java:606)
[testng] at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:80)
[testng] at org.testng.internal.Invoker.invokeConfigurationMethod(Invoker.java:564)
[testng] at org.testng.internal.Invoker.invokeConfigurations(Invoker.java:213)
[testng] at org.testng.internal.Invoker.invokeConfigurations(Invoker.java:138)
[testng] at org.testng.TestRunner.beforeRun(TestRunner.java:641)
[testng] at org.testng.TestRunner.run(TestRunner.java:609)
[testng] at org.testng.SuiteRunner.runTest(SuiteRunner.java:334)
[testng] at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:329)
[testng] at org.testng.SuiteRunner.privateRun(SuiteRunner.java:291)
[testng] at org.testng.SuiteRunner.run(SuiteRunner.java:240)
[testng] at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
[testng] at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:86)
[testng] at org.testng.TestNG.runSuitesSequentially(TestNG.java:1198)
[testng] at org.testng.TestNG.runSuitesLocally(TestNG.java:1123)
[testng] at org.testng.TestNG.run(TestNG.java:1031)
[testng] at org.testng.TestNG.privateMain(TestNG.java:1338)
[testng] at org.testng.TestNG.main(TestNG.java:1307)
我已经搜索了解决方案，要么降级firefox，要么升级selenium但是没有成功。
F.Y.I。 ：
Firefox版本：26.0 操作系统：Fedora 18 Selenium版本：2.39.0